Auxiliary circulation water pump for circulating water system

ABSTRACT

An auxiliary circulation water pump for circulating water system is provided, including a condenser having first and second ingress pipes and first and second egress pipes; first water pumps each having a capacity of 50% or 33.3% and connected to a first valve connected to the first ingress pipe; second water pumps each having a capacity of 3-10% and connected to a second valve connected to the second ingress pipe; and a control unit, which is operable, when all of the first water pumps shut down as machine set at standby state, to close the first valves and activates the second water pumps and the second valves, the second water pumps supplying water through the second ingress pipe into the condenser and then discharging through the second egress pipe, and also keeping vacuum of the condenser at design condition (say 7.45 kPaA).

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an industrial recirculation water cooling system, and more particularly to an auxiliary circulation water pump for circulating water system that offers effects of operation stability and energy saving.

DESCRIPTION OF THE PRIOR ART

For various plants or workshops, such as power plants, steam/electric co-generation plants, chemical works, and incineration plants, cooling medium, such as seawater, freshwater, and coolant, must be provided to a condenser for operation. In normal operation, large-capacity circulation water pumps are set in full-load operation in order to supply cooling water for condensation of the steam exhaust from a steam turbine and to keep vacuum of the condenser (around 7.45 kPaA) for ensuring output of the steam turbine. When the machine set is in a standby state, a primary steam stop valve of the steam turbine is closed as stipulated in operation guides. Therefore, the steam exhausts from the steam turbine into the condenser is cut off. Under such condition, only fraction of bypass steam, gland steam, vent piping steam, and drainage of condensate in steam pipe, etc. will be routed into the condenser. Since the thermal loading at machine set standby condition is far less than that at design point, the water flow demand for the circulation water system can be greatly reduced in order to lower the consumption of auxiliary power for the machine set in the standby state.

Referring to FIG. 1 , a conventional arrangement of circulating water system generally includes two circulation water pumps A of 50% or three recirculation water pumps A of 33.3% for full load operation. In a standby state, the circulation water flow demand could be less than 3% of the design flow at full load operation. In order to save auxiliary power, operators usually need to select one circulation water pump (of which the capacity is around 50% as an example for combined cycle power plant units) in operation. Operators can select to run the single pump at the design point or at minimum flow point (which is around 40% of the design flow or more; depending on equipment feature).

For operation being selected at the design point, pump operation can be kept more stable and the risk of system tripping could be relatively low as smooth flow regulation for target flow rate setting. However, the power consumption for such condition is extremely high (a single pump consuming around 2.5 MW; taking Tatan Power Plant gas-fired combined cycle units 1-6 of Taiwan Power Company as an example; each unit with 720 MW output) due to higher flow rate although higher pump efficiency around 90% at design point.

For operation being selected at the minimum flow point, the operation of the pump is relatively unstable, and the system flowrate regulation and control is relatively poor and the risk of tripping is relatively high. Once the circulation water pump trips, the circulation water system cannot be maintained and the vacuum of the condenser will be broken. Re-activation of the machine set requires re-establishing the circulation water system and re-building the condenser vacuum. Such re-activation is time-consuming and energy-consuming and affecting the capacity of power supply and machine set availability. While in minimum flow point operation, the efficiency of the pump is relatively poor (around 35%-45%) and the power consumption is only slightly different from that for the design point operation. Consequently, an operator often prefers to run single pump operating at the design point. Both cases lead to a high consumption of auxiliary power. Thus, the issue that the present invention is made to overcome is to reduce energy consumption for a machine set in a standby state and also to ensure stability of the machine set.

SUMMARY OF THE INVENTION

In view of the above problem, the present invention provides an auxiliary circulation water pump for circulating water system, which comprises: a condenser, which connects with a first ingress pipe, a second ingress pipe, a first egress pipe, and a second egress pipe; a plurality of first water pumps, which are each connected to a first valve, each of the first valves being connected to a first pipe interconnected with each other, each of the first pipes being connected to the first ingress pipe, each of the first water pumps having a capacity of 50% or 33.3%; a plurality of second water pumps, which are each connected to a second valve, each of the second valves being connected to a second pipe interconnected with each other, each of the second pipes being connected to the second ingress pipe of the condenser, each of the second water pumps having a capacity of 3-10%; and a control unit, which is operable, when all of the first water pumps shut down as machine set at standby state, to close each of the first valves and activates each of the second water pumps and each of the second valves, each of the second water pumps supplying water through each of the second pipes and the second ingress pipe into the condenser and then discharging through the second egress pipe, thereby, keeping vacuum of the condenser at design condition (say 7.45 kPaA).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a conventional circulation water system.

FIG. 2 is a schematic view showing a first embodiment of the present invention.

FIG. 3 is a schematic view showing a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

To expound the details of the present invention, as well as the efficacy achieved thereby, embodiments will be provided with reference to the drawings. Referring to FIG. 2 , an auxiliary circulation water pump for circulating water system according to a first embodiment of the present invention comprises:

a condenser 10, which comprises a first ingress pipe 11, a first egress pipe 13, and a second egress pipe 14, wherein the first egress pipe 13 is provided with a main butterfly valve 131, and the second egress pipe 14 is provided with a bypass valve 141;

a plurality of first water pumps 20, which are each connected to a first valve 21, wherein each of the first valves 21 is connected to a first pipe 22 interconnected with each other, and each of the first pipes 22 is connected to the first ingress pipe 11, and each of the first water pumps 20 has a capacity of 50% or 33.3%;

a plurality of second water pumps 30, which are each connected to a second valve 31, wherein each of the second valves 31 is connected to a second pipe 32 that is connected to the first pipes 22, and each of the second water pumps 30 has a capacity of 3-10%, wherein the bypass valve 141 has a design flowrate that corresponds to and matches with the capacity of each of the second water pumps 30; and

a control unit (not shown), which is operable, when each of the first water pumps 20 enters a standby state, to close each of the first valves 21 and the main butterfly valve 131 and subsequently activate each of the second water pumps 30 and each of the second valves 31, wherein each of the second water pumps 30 provides the condenser 10 to proceed with a circulation water operation and allows vacuum of the condenser 10 to be kept at design condition (say 7.45 kPaA), and each of the second water pumps 30 supplies water through the second pipe 32, the first pipe 22, and the first ingress pipe 11 into the condenser 10 and then discharging through the second egress pipe 14.

Referring to FIG. 3 , an auxiliary circulation water pump for circulating water system according to a second embodiment of the present invention is provided, which comprises: a condenser 10, which comprises a first ingress pipe 11, a second ingress pipe 12, a first egress pipe 13, and a second egress pipe 14, wherein the first egress pipe is provided with a main butterfly valve 131, and the second egress pipe 14 is provided with a bypass valve 141;

a plurality of first water pumps 20, which are each connected to a first valve 21, wherein each of the first valves 21 is connected to a first pipe 22 interconnected with each other, and each of the first pipes 22 is connected to the first ingress pipe 11, and each of the first water pumps 20 has a capacity of 50% or 33.3%, and each of the first water pumps 20 supplies water through each of the first pipes 22 and the first ingress pipe 11 into the condenser 10 and then discharging through the first egress pipe 13;

a plurality of second water pumps 30, which are each connected to a second valve 31, wherein each of the second valves 31 is connected to a second pipe 32 interconnected with each other, and each of the second pipes 32 is connected to the second ingress pipe 12 of the condenser 10, and each of the second water pumps 30 has a capacity of 3-10%, wherein the bypass valve 141 has a design flowrate that corresponds to and matches with the capacity of each of the second water pumps; and

a control unit (not shown), which is operable, when each of the first water pumps 20 enters a standby state, to close each of the first valves 21 and the main butterfly valve 131 and activate each of the second water pumps 30 and each of the second valves 31, wherein each of the second water pumps 30 supplies water through each of the second pipes 32 and the second ingress pipe 12 into the condenser 10 and then discharging through the second egress pipe 14, so that the bypass valve 141 allows vacuum of the condenser to be kept at design condition (say 7.45 kPaA), to thereby achieve an effect of stable operation and reduction of energy consumption; and

wherein the bypass valve 141 has a flowrate that corresponds to and matches with the capacity of each of the second water pumps 30, namely due to the capacity being 3-10%, each of the second water pumps is operable in collaboration with the bypass valve 141 that has a reduced flowrate in order to allows operation of each of the second water pumps 30 to be set through regulation of the flowrate of the bypass valve 141. 

I claim:
 1. An auxiliary circulation water pump for circulating water system, comprising: a condenser, which comprises a first ingress pipe, a second ingress pipe, a first egress pipe, and a second egress pipe; a plurality of first water pumps, which are each connected to a first valve, each of the first valves being connected to a first pipe interconnected with each other, each of the first pipes being connected to the first ingress pipe, each of the first water pumps having a capacity of 50% or 33.3%, each of the first water pumps supplying water through each of the first pipe and the first ingress pipe into the condenser and then discharging through the first egress pipe; a plurality of second water pumps, which are each connected to a second valve, each of the second valves being connected to a second pipe interconnecting with each other, each of the second pipes being connected to the second ingress pipe of the condenser, each of the second water pumps having a capacity of 3-10%; and a control unit, which is operable, when all of the first water pumps shut down as machine set at standby state, to close each of the first valves and activate each of the second water pumps and each of the second valves, each of the second water pumps supplying water through each of the second pipe and the second ingress pipe into the condenser and then discharging through the second egress pipe, and also keeping vacuum of the condenser at a predetermined level.
 2. The auxiliary circulation water pump for circulating water system according to claim 1, wherein the first egress pipe is provided with a main butterfly valve, and the second egress pipe is provided with a bypass valve, the bypass valve having a flowrate corresponding to and matching with the capacity of each of the second water pumps.
 3. An auxiliary circulation water pump for circulating water system, comprising: a condenser, which comprises a first ingress pipe, a first egress pipe, and a second egress pipe; a plurality of first water pumps, which are each connected to a first valve, each of the first valves being connected to a first pipe interconnected with each other, each of the first pipes being connected to the first ingress pipe, each of the first water pumps having a capacity of 50% or 33.3%; a plurality of second water pumps, which are each connected to a second valve, each of the second valves being connected to a second pipe, each of the second pipes being connected to the first pipes, each of the second water pumps having a capacity of 3-10%; and a control unit, which is operable, when all of the first water pumps shut down as machine set at standby state, to activate each of the second water pumps, each of the second water pumps providing the condenser to proceed with a circulation water operation and allowing vacuum of the condenser to be kept at a predetermined level, each of the second water pumps supplying water through each of the second pipes, the first pipe, and the first ingress pipe into the condenser and then discharging through the second egress pipe.
 4. The auxiliary circulation water pump for circulating water system according to claim 1, wherein the first egress pipe is provided with a main butterfly valve, and the second egress pipe is provided with a bypass valve, the bypass valve having a flowrate corresponding to and matching with the capacity of each of the second water pumps. 